Limited underthrusting of India below Tibet: He/He analysis of thermal springs locates the mantle suture in continental collision.

During continent–continent collision, does the downgoing continental plate underplate far inboard of the collisional boundary or does it subduct steeply into the mantle, and how is this geometry manifested in the mantle flow field? We test conflicting models for these questions for Earth’s archetypal continental collision forming the Himalaya and Tibetan Plateau. Air-corrected helium isotope data (3He/4He) from 225 geothermal springs (196 from our group, 29 from the literature) delineate a boundary separating a Himalayan domain of only crustal helium from a Tibetan domain with significant mantle helium. This 1,000-km-long boundary is located close to the Yarlung-Zangbo Suture (YZS) in southern Tibet from 80 to 92°E and is interpreted to overlie the “mantle suture” where cold underplated Indian lithosphere is juxtaposed at >80 km depth against a sub-Tibetan incipiently molten asthenospheric mantle wedge.

Geochemical evidence for fugitive gas contamination and associated water quality changes in drinking-water wells from Parker County, Texas.

Extensive development of horizontal drilling and hydraulic fracturing enhanced energy production but raised concerns about drinking-water quality in areas of shale-gas development. One particularly controversial case that has received significant public and scientific attention involves possible contamination of groundwater in the Trinity Aquifer in Parker County, Texas. Despite extensive work, the origin of natural gas in the Trinity Aquifer within this study area is an ongoing debate.

Hydrocarbon-Rich Groundwater above Shale-Gas Formations: A Karoo Basin Case Study.

Horizontal drilling and hydraulic fracturing have enhanced unconventional hydrocarbon recovery but raised environmental concerns related to water quality. Because most basins targeted for shale-gas development in the USA have histories of both active and legacy petroleum extraction, confusion about the hydrogeological context of naturally occurring methane in shallow aquifers overlying shales remains. The Karoo Basin, located in South Africa, provides a near-pristine setting to evaluate these processes, without a history of conventional or unconventional energy extraction.

Structural and Hydrogeological Controls on Hydrocarbon and Brine Migration into Drinking Water Aquifers in Southern New York.

Environmental concerns regarding the potential for drinking water contamination in shallow aquifers have accompanied unconventional energy development in the northern Appalachian Basin. These activities have also raised several critical questions about the hydrogeological parameters that control the naturally occurring presence and migration of hydrocarbon gases in shallow aquifers within petroliferous basins. To interrogate these factors, we analyzed the noble gas, dissolved ion, and hydrocarbon gas (molecular and isotopic composition) geochemistry of 98 groundwater samples from south-central New York.

Pre-drill Groundwater Geochemistry in the Karoo Basin, South Africa.

Enhanced production of unconventional hydrocarbons in the United States has driven interest in natural gas development globally, but simultaneously raised concerns regarding water quantity and quality impacts associated with hydrocarbon extraction. We conducted a pre-development assessment of groundwater geochemistry in the critically water-restricted Karoo Basin, South Africa. Twenty-two springs and groundwater samples were analyzed for major dissolved ions, trace elements, water stable isotopes, strontium and boron isotopes, hydrocarbons and helium composition.

Naturally Occurring versus Anthropogenic Sources of Elevated Molybdenum in Groundwater: Evidence for Geogenic Contamination from Southeast Wisconsin, United States.

Molybdenum (Mo) is an essential trace nutrient but has negative health effects at high concentrations. Groundwater typically has low Mo (<2 μg/L), and elevated levels are associated with anthropogenic contamination, although geogenic sources have also been reported. Coal combustion residues (CCRs) are enriched in Mo, and thus present a potential anthropogenic contamination source.

A reconnaissance analysis of groundwater quality in the Eagle Ford shale region reveals two distinct bromide/chloride populations.

The extraction of oil and natural gas from unconventional shale formations has prompted a series of investigations to examine the quality of the groundwater in the overlying aquifers. Here we present a reconnaissance analysis of groundwater quality in the Eagle Ford region of southern Texas. These data reveal two distinct sample populations that are differentiable by bromide/chloride ratios.